Method for monitoring the wear and extending the life of blast furnace refractory lining

Abstract

A method is provided for extending the life of a refractory lining of a blast furnace hearth. The refractory hearth has temperature probes embedded in the floor and walls thereof. The method includes periodically measuring temperatures indicated by the probes and determining the campaign maximum and current average temperature readings to locate two solidification isotherm representing the wear line of the refractory and the inner surface of the protective metal layer. The thickness of the protective layer is determined from the distance between the solidification isotherms representing the refractory wear line and the inner surface of the metal skull. From this determination sufficient thickness of the protective layer is maintained during actual operation of the furnace.

We claim: 
     
       1. A method of extending the life of a refractory lining of a blast furnace hearth, wherein the refractory lining of said hearth has temperature probes embedded at spaced locations in radial directions from the center of the furnace hearth and at various elevations across the thickness of the floor and walls of the furnace hearth, comprising the steps of: a. periodically measuring temperatures at said spaced locations in said radial directions and across the thickness of the refractory lining of the hearth by the temperature probes embedded therein;   b. determining the maximum temperature recorded by each temperature probe since the beginning of a campaign of the furnace and the average temperature recorded by each temperature probe during a current time period;   c. analyzing the relation of said campaign maximum and current average temperatures of said temperature probes embedded in the hearth walls correlated with the radial distance between the temperature probes and the center of the furnace hearth and the relation of said campaign maximum and current average temperatures of said temperature probes embedded in the hearth floor correlated with the elevation distance between the temperature probes and the floor so as to predict the location of the wear line of the refractory lining from the location of a solidification isotherm closest to a metal shell, and to predict the location of the inner surface of a protective layer of solidified metal skull lining said refractory hearth from an isotherm closest to the hot side of the furnace remote from the metal shell,   d. determining the thickness of the solidified metal skull during actual furnace operation from the distance between the wear line of the refractory lining and the inner surface of the metal skull, and   e. maintaining sufficient thickness of said protective layer of solidified metal skull during operation of said furnace to extend the life of the refractory lining of said furnace hearth.   
     
     
       2. A method according to claim 1 wherein said analysis is carried out by estimating the location of said solidification isotherms using a one dimensional heat transfer approximation, using this approximation as the initial boundary to begin a moving boundary calculation from a two dimensional heat transfer model, and continuing to iterate the two dimensional heat transfer model until a final boundary of each solidification isotherm is determined by minimizing the difference between the measured temperature at each temperature probe location and a predicted temperature at sad-location based on iterations of the two dimensional heat transfer model. 
     
     
       3. A method according to claim 1 further comprising temperature probes embedded in a water cooled metal shell of the furnace hearth aligned at the same elevation with the temperature probes in the furnace hearth walls, and wherein said step of maintaining a protective layer includes the step of maintaining adequate heat transfer from the refractory hearth walls to the metal shell of the furnace hearth and from the metal shell to cooling water applied to the metal shell; said step of maintaining adequate heat transfer including determining a first temperature at the interface between the refractory lining of the hearth and the metal shell from the temperature difference between at least two temperature probes aligned in a radial direction in the refractory hearth walls, said first interface temperature being designated TIR; determining a second temperature at said interface from the summation of the temperature of at least one of the temperature probes embedded in the metal shell and the temperature difference between said temperature probes aligned in the same radial direction as the temperature probe in said shell, said second interface temperature being designated TIS; comparing the values of TIR and TIS to determine the difference there between; and in the event of a substantial difference between TIR and TIS taking corrective action to minimize the difference.